Rocking dynamic damper with floating pin support



April 11, 1939. R. CHILTON 2,154,063

ROCKING DYNAMIC DAMPER WITH FLOATING PIN SUPPORT Filed July 8, 1937 4 iiiiiimimiu INVENTOR XoLAND C'JYJLTQN '1 '1 ATTORNE I Patented Apr. 11, 1939 PATENT ornca ROCKING DYNAMIC mmna'wrrn FLOAT- I me rm surron'r Roland Chilton, Ridgewood, N. 1., assignor, by

mesne assignments, to Wright Aeronautical Cor- V poration, Paterson, N. J., a corporatlolfof New York Application July 8, 1937, Serial No. 152,492

16 Claims.

This invention relates to dynamic pendulum dampers for suppressing torsional vibrations andin certain respects comprises improvements in my co-pending application, Serial No. 41,541. In that application it is set forth that a'pendulum mounted on a rotating shaft so as to be stabilized by centrifugal force has the same number of swings per revolution at all speeds of revolution wherefore, if the pendulum frequency be made equal to the number of disturbing impulses per revolution to which the shaft is subject in operation the pendulum automatically swings 180 out of phase with these disturbing impulses which---' are, accordingly neutralized to the suppression of torsional vibrations.

It is also pointed out that large dampening masses are desirable with which it becomes impossible to obtain a sumciently fast pendulum frequency with a simple single pivotal suspension, due to the large radiusof gyration of the counterweight masses. It is known that the fastest frequency that can be obtained with a simple single pivot pendulum is when the pivot is located at the radius of gyration of the pendulum mass, which in the case illustrated is over 3", and this gives a frequency many times too slow for synchronism with the impulses to which the crankshaft is subject.

Accordingly, the application referred to teaches the use of a rocker type of suspension wherein blocks having convex and concave arcuate surfaces are organized to rockably support the counterweight upon the crankshaft and it is there shown that by selecting the appropriate relative curvature of the rocking faces, the desiredhigh frequency of pendulum vibration may be obtained. As the rockably contacted supporting faces are made to closer relative arcuity. the travel of their contact point during rocking'action, through a given small angle, increases. This contact shift determines the arm at which the centrifugal force acts to restore the weight when it hasbeen displaced and, accordingly, by suitably selecting the relative radii of the rocking faces, the desired high frequency may be achieved in spite of the large polar moment of the weight.

It will be seen that the heavy centrifugal forces act through a rocking contact point that shifts rapidly from side to side; these rapidly shifting forces react upon the attachment between the rocker members and the parts to which they are secured, tending to set up scuilingdue to the deflection of the parts under the high loads involved.

Accordinglma prime object of the present invention is to provide a simplified structure which shall be easy of manufacture and in which the rockably contacted members are so formed that there will be no tendency for them to chafe against the associated parts. Another object of the invention is to provide improved and frictionless means for preventing lateral displacement of the weight and so to confine the action to rocking, as distinguished from sliding, contact'shift. Othenobjects and advantages will be obvious fromthe following description with reference to the drawing in which similar numbers indicate similarparts and in which, I V

Fig. 1 is an end view in part section of a crankshaft equipped with the improved counterweight suspension;

Fig. 2 is a longitudinal view in part section on the line 2-2 of Fig. 1;

Fig. 3 is a fragmentary plan view; Fig. 4 is a fragmentary section of an alternate rocking device, and Fig. 5 is a fragmentary end view of Fig. 4;

In the drawing ll'l designates a crankpin of a conventional crankshaft to which is secured a rear crank cheek I! by the usual pinch bolt l4. The cheek l 2 is provided with the usual rear journal l6 and with an extension member l8 which is pierced by a large hole in which ispreferably floatingly disposed a large diameter pin or trunnlon 20 to carry which a bushing 22 is preferably employed. The counterweight has two similar halves 24 having bushings 26 and secured together around the extension l8 by means of the bolts 28. It will be seenthat the bore radius of the bushings 2B is greater than that of the supporting pin 20 so that, at the contact point "1? (Fig. l) a rocking relation exists between the pin and counterweight whereby the contact point travels on either side of the center line 22 as the weight oscillates. The radius of the pin 20 has been designated as r and that of the engaged bushing 26 as R and the relationshi ,of these radii is so chosen as to give the desired high frequency of vibration notwithstanding the large radius of gyration of the weight.

It is'a feature of this construction that the action between the pin 20 and the bushings 26 at the counterweight is one of rolling or rocking as distinguished from sliding contact. Thisis an important point and is therefore emphasized as follows: When a cylindrical member is oscillated in a hole or bushing with which it has a mere running clearance, the action is necessarily in volved would introduce undesirable friction or wear. On the other hand, it will be seen that there is a substantial difference between the radii R and r with the result that, for the small angles of swing here contemplated, (of theorder of 1 on each side of center) the action will be pure rolling exactly as in the contact between a rocking chair and the floor, there being no sliding at the surfaces. To insure this last result, means are provided, according to this invention, to prevent end motion of the weight in the plane of Fig. 1,

this means being shown in Fig. 1 to comprise flexible plates 30, an end of one of which is seen in plan view in Fig. 3. The inner ends of these plates are rgiidly secured to the extension I. by screws 32 and the outer ends are rigidly secured to the counterweight 24 by bolts 34.

It is again mentioned that, by using the entire normal counterweight mass of the radial engine crankshaft as'the dynamic damper mass, the required amplitude of vibration is quite small, as indicated by the clearance at Y which is intended to be greater than the normal amplitude of swing. The flexible plates 30, accordingly, yield this small amount by bendingflexure but are rigid in tension. To prevent sliding at the contact point or zone "X, it is necessary that these plates be placed on the line passing through this point or zone, as indicated at Z".

Figs. 4 and 5 are detail views illustrating an alternate embodiment wherein struts 36 have spherical ends, indicated by the radius .8, engage against a suitable abutment 38 on the crankshaft and against an adjustment screw 4| which may be locked in adjusted position in the counterweight by the pinch bolt 42. The abutments 38 embrace the crankshaft l2, being con- .veniently formed onthe back plate 44 of a splined bushing 48 used for driving a crankshaft extension shaft (not shown).

It is known that the reactions between any two contacting surfaces must be at right angles to each surface and, in the case of arcuate surfaces,-

creep under the high speed vibration of weight whereby to distribute the wear around the entire circumference.

' It will be seen .thatthis construction is economical in manufacture since it involves the con-' struction of simple cylindrical holes in both the counterweight and the crankshaft extension to receive the floatingbushings and that no means are needed to anchor these parts against rotation; in fact, preferably they should be free to float. While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in' the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

' I claim as my invention:

1. In combination with a crankshaft member and a counterweight member, one embracing the other, having a single opening'formed in each member, the opening in one member being substantially bigger-than that in the other, a single cylindrical cross pin comprising a rocker block closely fitted to the wall ofthe smaller opening and loosely engaging the wall of the larger opening for rocking as distinguished from-sliding action, and flexible means connecting said members to suppress relative sliding therebetween.

2. The combination with a crankshaft member and a counterweight member, one embracing the other, having a single opening in each, of a single cylindrical member closely fitted to the wall of one of said openings but loosely engaging the wall of the other opening for rocking as distinct from sliding contact, of the counterweight member relative to the crankshaft member and flexible means connecting said members to suppress relative sliding therebetween.

3. In combination, a. crankshaft member, a single cylindrical pin extending therefrom, a counterweight member loosely embracing said crankshaft member and including openings, having surfaces of larger diameter than said pin, the surfaces of said openings being engaged with the pin for rocking, as distinct from sliding motion, and flexible means connecting said members to suppress lateral movement therebetween but to allow of relative polar displacement.

4. In combination, a crankshaft. extension member having an opening including a wall, a cylindrical member fittedto said wall, a counterweight member having a larger opening, including a wall loosely engaging said cylindrical mem ber for rocking contact as distinct from sliding action and means in line with the zone of rocking contact to prevent lateral motion of said counterweight to confine the action between said pin and counterweight opening wall to non-sliding rocking shift of the zone of contact thereof.

5. In combination, a crankshaft extension member having an opening, a cylindrical member fitted closely to the wall of said opening and extending therefrom, a counterweight having larger openings including walls loosely rockably contacting said extension, and means aligned with the zone of rocking contact to prevent the counterweight from sliding laterally.

6. In combination, a crankshaft member and a counterweight member having an opening including a wall, in each, the radius of curvature of one'wall being greater than of the other, a cylindrical member closely fitted to the wall of the smaller opening and loosely rockably engaging the wall of the larger opening, and means aligned with the zone of rocking engagement preventing sliding of the wall of the large opening on the cylindrical member whereby the weight is anti-frictionally rockably supported for pendulous vibration.

7. A crankshaft extension having an opening including a wall, a pin fitted thereto extending beyond respective faces of the extension, counterweight halves having circular recesses of larger diameter than said pin, said halves embracing the extension with the extended pin ends engaging the walls of respective recesses in said halves, and means between the extension and the assembled halves yieldable to rocking movement of the counterweight relative to the extension but non-yieldable to translational tendencies therebetween.

8. In combination, a crankshaft extension member and a counterweight member, one embracing the other for relative movement, including primary rockably contacted means supporting ment, and secondary flexible means connecting said members for suppressing relative bodily translation between said members, said secondary means being freely yieldable to relative rocking movement of said members.

9. In combination, a crankshaft extension member and a counterweight member, one embracing the other for relative movement, said members having openings of different diameter, including walls, a pin fitted for rotation only on the wall of the smaller opening and rockably contacted with the wall of the larger opening whereby one member is free to rock in rolling contact upon said pin, said pinbeing free to creep rotationally in the other member for the suppression of scuiflng at the rockably contacted portion of said pin and one memberr 10.. In combination, a crankshaft extension member and a counterweight member, one embracing the other for relative movement, said members having openings of different diameter, including walls, a pin fitted for rotation only on the wall of the smaller opening and rockably contacted with the wall of the larger opening whereby one member is free to rock in rolling contact upon said pin, said pin being free to creep rotationally in the other member for the suppression of scufling at the rockably contacted portions of said pin and one member, and opposed means, aiined on a tangentv to the rockably contacted portions, said means being unyieldable on the tangent axis and yleldable along other axes and being attached at their ends to respective members'.

' 11. In combination, a crankshaft extension member having a pin floatingly fitted thereto and extendingbeyond the end faces thereof,a counterweight member embracing said extension and having circular-recesses, and floating bushingsengaged in said recesses, said bushings having openings of larger diameter than the diameterof said pin and engaging same for rocking contact therewith, said pin serving-as a support for said counterweight member against the action of centrifugal force.

' 12.- In combination, a crankshaft extension member having a pin floatingly fitted thereto and extending beyond the end faces thereof, a counterweight member embracing said extension and having circular recesses, and floating bushings engaged in said recesses, said bushings having opening of larger diameter than the diameter of said pin and engaging same for rocking contact therewith, said pin serving as a support for said counterweight member against the action of centrifugal force, and flexible means connectingsaid member to confine same to relative polar movement without translation.

13. In combination, a crankshaft extension member and a counterweight member, one embracing the other, a pin fioatingly engaged in one member and extending therebeyond, and rings of larger diameter than the pin rockably contacted with the extending portions thereof and floatingly engaged in the other member.

14. In combination, a crankshaft extension member and a counterweight member, one embracing the other, a pin floatingly engaged in one member and having concentric end portions extending beyond the confines of the member, and rings having an inside diameter larger than that of the pin end portions rockably engaged with said end portions, said rings being floatingly engaged by the other said member.

15..In combination, a crankshaft extension member and a counterweight member; one em bracing the other, a pin floatingly engaged in one member and having concentric end portions extending beyond the confines of the member, rings having an inside diameter larger than that of the pin end portions rockably engaged with said end portions, said rings being floatingly engaged by the other said member, and means, substantially alined with the zone of rocking engagement of said rings and pin portions, connecting said members for restraining same against lateral displacement but permitting of relative polar displacement of said members.

16. In combination, a crankshaft extension member and a counterweight member, one embracing the other, a pin fioatingly engaged in one member and-having concentric end portions ex tending beyond the confines of themember, and

rings having an inside diameter larger than that ofthe pin end portions rockably engaged with said end portions, said rings being floatingly engaged by the other said member, and means, substantially aiined with the zone of rocking engagement of said rings and pin portions, connecting said members for restraining same against lateral displacement but permitting of relative polar displacement of said members, said connecting means comprising flexible links, substantially fixed in length, attached at respective ends to the embracing and embraced members.

ROLAND CHILTON. 

